Study On Preparation Of Yttrium Aluminum Garnet(YAG) Transparent Ceramics

Compared with single crystals,transparent ceramics have many advantages,such as low preparation cost,large size,high doping concentration and so on.These made transparent ceramics become a hotspot research in recent years.Yttrium aluminium garnet(Y3Al5O12,YAG)transparent ceramics are widely used in solid-state lasers,transparent armor,and fluorescent illumination because of their excellent thermophysical properties and outstanding optical properties.These excellent properties make them become critical materials in the field of optical function.In this paper,YAG powders were synthesized by solid-state reaction method using nano-Al2O3 and Y2O3 powders as raw materials.The effects of raw materials conditions and reaction process control on the phase structure and particle size of the synthesized powders were studied.The YAG transparent ceramics were prepared by combining hotpressure sintering and vacuum pressureless sintering.The effects of sintering process on densities,tissue morphology and optical properties of the ceramics were studied.The results of the study are as follows:1.YAG powder was synthesized by solid-state reaction method.With the increasing solid-state reaction temperature,the phase of reaction product transformed from YAM(intermediate product)to YAP(intermediate product)and finally changed to YAG.The content of YAG phase in the synthesized powder reaches 96.2%when the reaction temperature is 1400℃ and the reaction time is 2 h.Moreover,the powder has sufficient grain growth and clear grain boundary.After being planetary ball milled at 160 rpm,the particle size distribution of powder is uniform,and the particles of powder is fine.When the Nd doping amount is 1%,the intensity of the most substantial diffraction peak of the powder is the highest,and the grain size of the powder is calculated to be 51.78 nm.These indicat that the crystallinity of the powder is better and the grain growth is more adequate.2.The YAG powder synthesized by the solid-state reaction method was used as raw material.1 wt%LiF was added as sintering aid.The YAG translucent ceramics was sintered by vacuum hot-pressing.The hot-pressing temperature is 1500℃.The heating rate is 4℃/min.The holding time is 2 h.The hot-pressing pressure is 40 MPa.The average grain size of YAG translucent ceramics is 5.40 μm,and its microstructure is ecplict.The optical transmittance of the ceramic sample was 20.089%at 400 nm and was 23.957%at 1064 nm.3.The YAG powder synthesized by the solid-state reaction method was raw material.0.5 wt%ethyl orthosilicate(TEOS)and 0.1 wt%MgO were added as sintering aids.Ceramic embryo was formed by 40 MPa molding combined with 200 MPa cold isostatic pressing.The ceramic embryo was pressurelessly sintered at 1750℃ for 5h in vacuum.After that,the YAG transparent ceramics were obtained.The grain of YAG transparent ceramics is clear,and the grain growth is full.The optical transmittance of the ceramic samples was 52.595%at 400 nm and was 60.712%at 1064 nm.The nano-hardness of the ceramics reached the maximum value of 25.87 GPa.